Direct manipulation of FFD: efficient explicit solutions and decomposible multiple point constraints

Published online: 25 July 2001     

A carbon monoxide sensor based on single-walled carbon nanotubes doped with copper chloride

A carbon monoxide gas sensor based on single-walled carbon nanotube(SWCNT)has been developed for detection of carbon monoxide(CO)at room temperature.Copper chloride(CuCl)was mixed with SWNT by mechanical blending.The thin film was deposited on interdigitated electrodes by using airbrush technology.This paper described the fabrication of the sensor for detecting carbon monoxide with concentrations from 20 ppm to 100 ppm.The performance of CO gas sensor was measured by using relevant apparatus to obtain the continuous sensor electric resistance change on exposure to CO and air atmosphere at room temperature,respectively.The results exhibited that the senor presented a larger sensitivity and a good recoverability.The experimental results suggested the potential use of CuCl doped SWCNT for CO detecting.     

Automatic upright orientation and good view recognition for 3D man-made models

Many graphics applications require that 3D models automatically be presented upright and from a good view. We propose a method that simultaneously recognizes upright orientation and good view for 3D man-made models. The strategy is to determine the best base on which a 3D model can stand upright from a small set of candidate bases. Every candidate base is composed of clustered facets of the simplified convex hull of the given 3D model. Next, a proposed UV-measurement selects the best base from the candidate bases using weighted feature-based evaluation functions based on geometrical, physical, and visual aspects. Our method has been tested using a public 3D model database and compared with previous methods. As experimental results show, our method outperforms previous work in both efficiency and accuracy.     

劳动力转移背景下的种植业结构调整

对1990～2010年我国农业劳动力和5种主要农作物播种面积进行的分析表明,农村劳动力转移首先对我国的粮食生产造成很大影响,粮食种植主要集中于几个劳动力流出省份,面积总体上呈下降趋势.与此同时,收益较高的经济作物种植面积比重大幅上升.可能的解释是,在经营规模普遍较小、劳动力素质偏低的情况下,作为理性的经营者,农户进行生产结构调整时往往较少考虑自身劳力的成本,而更为关注农作物的收益.粮价偏低直接影响了种粮农民的收益,进而影响其种粮积极性.     

The effect of MWCNTs on the performance of α-sexithiophene OTFT device and its gas-sensing property

In this paper,bottom contact organic thin-film transistor(OTFT)gas sensors were prepared.Silicon dioxide(SiO2)and titanium/aurum(Ti/Au)were used as the insulating layer and the electrode for the device,respectively.The multi-walled carbon nanotubes(MWCNTs)/α-sexithiophene(α-6T)bilayer films were used as the active layer,andα-6T single layer sensitive film was also prepared for comparison purpose.The electrical and trace NO2-sening properties of these two OTFT gas sensors were tested and analyzed.The results showed that,the OTFT device based on MWCNTs/α-6T bilayer had obviously better electrical properties,better stabilities and higher NO2-sening response values than the device withα-6T single layer,in which both the carrier mobility(μ)and on/off current ratio enhanced two order of magnitude.The improved performance of bilayer OTFT can be explained that MWCNTs acted as highly conducting bridges connecting the crystalline terraces in theα-6T film.Threshold voltage(VT),carrier mobility,on/off current ratio and grid current which showed extremely similar variation trend as source-drain current,were optional parameters to reveal the gas-sensing characteristic of OTFT gas sensors.Morphology analysis showed that the special feature of MWCNTs had certain influence on the gas-sensing properties.     

Gaseous and electrochemical hydrogen storage kinetics of as-quenched nanocrystalline and amorphous Mg2Ni-type alloys

The nanocrystalline and amorphous Mg₂Ni-type Mg₂Ni_1?x Co _x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by melt quenching technology. The structures of the as-cast and quenched alloys were characterized by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The alloy electrodes were charged and discharged with a constant current density in order to investigate the electrochemical hydrogen storage kinetics of the alloys. The results demonstrate that the substitution of Co for Ni results in the formation of secondary phases MgCo₂ and Mg instead of altering the major phase Mg₂Ni. No amorphous phase is detected in the as-quenched Cofree alloy, however, a certain amount of amorphous phase is clearly found in the as-quenched alloys substituted by Co. Furthermore, both the rapid quenching and the Co substitution significantly improve the gaseous and electrochemical hydrogen storage kinetics of the alloys, for which the notable increase of the hydrogen diffusion coefficient (D) along with the limiting current density (I _L ) and the obvious decline of the electrochemical impedance generated by both the Co substitution and the rapid quenching are basically responsible.     

用流延法制备优质陶瓷基片的研究

本文概括了流延成型工艺的现状，介绍了有机基流延成型工艺中溶剂及添加剂的作用和选择原则，同时介绍了几种新的流延成型工艺。     

一种16QAM调制实现技术的研究

讨论了16QAM调制时应用不同类型和参数的滤波器对系统性能的影响．针对16QAM的特点，采用了存储波形累加求和法来代替一般的滤波成形，提高了调制速度．并利用其相位对称的特点将波形存储表压缩为原容量的1／4，有效地节约了存储空间．     

小电流接地系统的讨论

对小电流接地系统单相接地原理进行了分析，对其国内外的研究现状进行了归纳总结，最后对故障选线原理的研究进行了展望。